EBS is a lymphotropic herpes virus that infects and persists in human B lymphocytes and epithelial cells. EBV has been associated with infectious mononucleosis (IM) and two malignancies, Burlitt's lymphoma (BL) and nasopharyngeal carcinoma (NP). The clinical diagnosis of IM relies upon the simultaneous presence of fever, pharyngitis, lymphocytosis with atypical lymphocytes and a positive serology. Presently, the presence of heterophil antibodies in patient sera is highly suggestive of IM. However, the test is not conclusive as the production of heterophil antibodies during human infection is at best only 90 percent, and other viral infections also induce such antibodies. A superior serodiagnostic method is to detect antibodies to the EBV-VCA. The specific aims of this proposal are to: l) purify and characterize recombinant VCA polypeptides, 2) develop a microwell ELISA format using recombinant VCA antigens, 3) determine sensitivity, specificity and reproducibility of this rapid antigen-detection ELISA compared to other immunodiagnostic assays for IM, and 4) determine specificity of the ELISA using a variety of blood specimens from patients with related infections and diseases.